Definition of Maxwell's Laws of Electromagnetism

Maxwell's laws of electromagnetism consist of four differential equations that describe electric and magnetic fields, their sources, charge density, and current density. Taken together, the equations show that electricity, magnetism, and light are all manifestations of a single phenomenon known as an electromagnetic field. James Clerk Maxwell found that a changing magnetic field induces a changing electric field and vice versa, so that together such fields could propagate through space forever. He found that the speed calculated for electromagnetic waves, based on experiments on charges and currents, exactly matched the speed of light. By compiling these four separate equations and understanding them together, Maxwell unified the fields of electromagnetism and optics (although he contributed to one equation directly, three had already been fully derived).